Electrophotographic plate and process employing photoconductive charge transfer complexes



United States Patent 3,408,190 ELECTROPHOTO GRAPHIC PLATE AND PRO C- ESSEMPLOYING PHOTOCONDUCTIVE CHARGE TRANSFER COMPLEXES Joseph Mammino,Penfield, N.Y., assignor to Xerox Corporation, Rochester, N.Y., acorporation of New York No Drawing. Filed Mar. 15, 1966, Ser. No.534,417 21 Claims. (CI. 96-15) ABSTRACT OF THE DISCLOSUREPhotoconductive materials are prepared from polysulfone resins and Lewisacids. The materials are charge transfer complexes. The photoconductivematerials are used to make electrophotographic plates. Methods of usingthe plates are also disclosed.

This invention relates to photoconductive materials, and moreparticularly, to their use in electrophotography.

It is known that images may be formed and developed on the surface ofcertain photoconductive materials by electrostatic means. The basicXerographic process, as taught by Carlson in US. Patent 2,297,691,involves uniformly charging a photoconductive insulating layer and thenexposing the layer to a light-and-shadow image which dissipates thecharge on the areas of the layer which are exposed to light. Theelectrostatic latent image formed on the layer corresponds to theconfiguration of the light-and-shadow image. Alternatively, a latentelectrostatic image may be formed on the plate by charging the plate inimage configuration. This image is rendered visible by depositing on theimage layer a finely divided electroscopic marking material called atoner. The powder developing material will normally be attracted tothose portions of the layer which retain a charge, thereby forming apowder image corresponding to the latent electrostatic image. Thispowder image may then be transferred to paper or other receivingsurfaces. The paper then will bear the powder image which maysubsequently be made permanent by heating or other suitable fixingmeans. The above general process is also described in US. Patents2,357,809; 2,891,011; and 3,079,342.

That various photoconductive insulating materials may be used in makingelectrophotographic plates is known. Suitable photoconductive insulatingmaterials such as anthracene, sulfur, selenium or mixtures thereof, havebeen disclosed by Carlson in US. Patent 2,297,691. These materialsgenerally have sensitivity in the blue or near ultra-violet range, andall but selenium have a further limitation of being only slightly lightsensitive. For this reason, selenium has been the most commerciallyaccepted material for use in electrophotographic plates. Vitreousselenium, however, while desirable in most aspects, suffers from seriouslimitations in that its spectral response is somewhat limited to theultra-violet, blue and green regions of the spectrum, and thepreparation of vitreous selenium plates requires costly and complexprocedures, such as vacuum evaporation. Also, selenium plates requirethe use of a separate conductive substrate layer, preferably with anadditional barrier layer deposited thereon before deposition of theselenium photoconductor. Because of these economic and commercialconsiderations, there have been many recent efforts towards developingphotoconductive insulating materials other than selenium for use inelectrophotographicplates.

It has been proposed that various two-component materials be used inphotoconductive insulating layers used in electrophotographic plates.For example, the use of inorganic photoconductive pigments dispersed insuitable binder materials to form photoconductive insulat- "ice inglayers is known. It has further been demonstrated that organicphotoconductive insulating dyes and a wide variety of polycycliccompounds may be used together with suitable resin materials to formphotoconductive insulating layers useful in binder-type plates. In eachof these two systems, it is necessary that at least one originalcomponent used to prepare the photoconductive insulating layer be,itself, a photoconductive material.

In a third type plate, inherently photoconductive polymers are used;frequently in combination with sensitizing dyes or Lewis acids to formphotoconductive insulating layers. Again, in these plates at least onephotoconductive component is necessary in the formation of the layer.While the concept of sensitizing photoconductors is, itself,commercially useful, it does have the drawback of being limited to onlythose materials already having substantial photoconductivity.

The above discussed three types of known plates are further described inUS. Patents 3,097,095; 3,113,022; 3,041,165; 3,126,281; 3,073,861;3,072,479; 2,999,750; Canadian Patent 644,167; and German Patent1,068,115.

The polymeric and binder-type organic photoconductor plates of the priorart generally have the inherent disadvantages of high cost ofmanufacture, brittleness, and poor adhesion to supporting substrates. Anumber of these photoconductive insulating layers have low temperaturedistortion properties which make them undesirable in an automaticelectrophotographic apparatus which often includes powerful lamps andthermal fusing devices which tend to heat the plate. Also, the choice ofphysical properties has been limited by the necessity of using onlyinherently photoconductive materials.

Inorganic pigment-binder plates are limited in usefulness because theyare often opaque and are thus limited to use in systems where lighttransmission is not required. Inorganic pigment-binder plates have thefurther disadvantage of being non-reusable due to high fatigue and roughsurfaces which make cleaning difficult. Still another disadvantage isthat the materials used have been limited to those having inherentphotoconductive insulating properties.

It is therefore an object of this invention to provide a photoconductiveinsulating material suitable for use in an electrophotographic platedevoid of the above noted disadvantages.

Another object of this invention is to provide an economical method forthe preparation of photoconductive insulating materials wherein none ofthe required components is by itself substantially photoconductive.

Another object of this invention is to provide a photoconductiveinsulating material suitable for use in electrophotographic plates inboth single use and reusable systems.

Yet another object is to provide a photoconductive insulating layer foran electrophotographic plate which is substantially resistant toabrasion and has a relatively high distortion temperature.

Yet a further object of this invention is to provide anelectrophotographic plate having a Wide range of useful physicalproperties.

A still further object of this invention is to provide photoconductiveinsulating layers which may be cast into self-supporting binder freephotoconductive film and structures.

Still another object of this invention is to provide a novel combinationof initially non-photoconductive insulating materials suitable for usein the manufacture of the photoconductive insulating layer of aXerographic plate which are easily coated on a desired substrate orcombined with a conductive layer.

Another object is to provide a transparentself-supportingphotoconductive film. adaptedforxerographic imagcurringunits having the formula R r w l l; O A O L R2 I I i in R and R are eachselected from the group consisting wherein:

of hydrogen and alkyl radicals, the total number of carbon atoms in Rand R being up to 12; and

\ n is an integer having a value of at least two.

The above described complex may comprise from 1 to about 100 parts ofresin for every one part of Lewis acid. About 1 to about 4 parts resinfor each part Lewis acid is preferred as producing a plate with the mostdesirable combination of photoconductive sensitivity and reusability.Best results have been obtained when using a complex comprising2,4,7-trinitro-9-fluorenone as the Lewis acid and the resin obtained byreacting the potassium or sodium salt of bisphenol-A with p,p'-dichlorodiphenylsulfone in dimethylsulfoxide and chlorobenzene. This synthesisis described in detail in Dutch Patent 6,408,130.

It should be noted that neither of the above two'components (A and B)used to make the photoconductor of this invention is by itselfphotoconductive; rather, they are each non-photoconductive.

After the above substantially non-photoconductive Lewis acid is mixed orotherwise complexed with said substantially non-photoconductive resinousmaterial, the highly desirable photoconductive insulating material isobtained which may be either cast as a self-supporting layer or may bedeposited on a suitable supporting substrate. Any other suitable methodof preparing a photoconductive plate from the above photoconductivematerial may be used. 7

It has been found by the present invention that electron acceptorcomplexing may be used to render inherently non-photoconductive electrondonor type insulators photoconductive. This greatly increases the rangeof useful materials for electrophotography.

A Lewis acid is any electron acceptor relative to other reagents presentin the system. A Lewis acid will tend to accept a pair of electronsfurnished by an electron donor (or Lewis base) in the process of forminga chemical compound or, in the present invention, a charge transfercomplex.

A Lewis acid is defined for the purposes of this invention as anyelectron accepting material relative to the polymer to which it iscomplexed.

A charge transfer complex may be defined as a molecular complex betweensubstantially neutral electron donor and acceptor molecules,characterized by the fact that photoexcitation produces internalelectron transfer to yield a temporary excited state in which the donoris more positive and the acceptor more negative than in the groundstate.

It is believed that the donor-type insulating resins of the presentinvention are rendered photoconductive by the formation of chargetransfer complexes with electron acceptors, or Lewis acids, and thatthese complexes, once formed, constitute the photoconductive elements ofthe plates.

. Broadly speaking, charge transfer complexes are loose V associationscontaining electron donors and acceptors,

frequently in stoichiometric ratios, which are characterized as follows:

(A) Donor-acceptor interaction is weak-in the neutral ground state,i.e., neither donor nor acceptor is appreciably perturbed by the othervin the. absence of photoexcitation. I 1

(B) Donor-acceptor interaction is relatively strong in the photo-excitedstate, i.e., the components are at least partially ionized byphoto-excitation.

(C) When the complex .is formed, one or more new absorption bands,appear in the, near ultra-violet or visible region (wavelengths between32004500 Angstrom units) which are present in neither donor alone noracceptor alone, but which are instead a property of thedonor-acceptor-complex.

It is found that both the intrinsic absorption bands of the donor andthe charge transfer bands of the complex may be used to excitephotoconductivity.

Photoconductive insulator for the purposes of this invention is definedwith reference to the practical appli-. cation in electrophotographicimaging. It is generally considered that any insulator may be renderedphotoconductive through excitation by sufiiciently intense radiation ofsufficiently short wavelengths. This statement applies generally toinorganic as well as to organic ma-. terials, including the inert binderresins used in binder plates, and the electron acceptor type activatorsand aromatic resins used in the present invention. However, the shortwavelength radiation sensitivity is not useful in practical imagingsystems because sufiiciently intense sources of wavelengths below 3200Angstrom unitsare not available, because such radiation is damaging tothe human eye and because this radiation is absorbed by glass opticalsystems. Accordingly, for the purposes of this application, the termphotoconductive insulator includes only those materials which may becharacterized as follows:

(1) They may be formed into continuous films which. are capable ofretaining an electrostatic charge in the absence of actinic radiation.

(2) These films are sufficiently sensitive to illumination ofwavelengths longer than 3200 Angstrom units to be discharged by at leastone half by a total flux of at most 10 quanta/cm. of absorbed radiation.

This definition excludes the resins and Lewis acids of my disclosure,when used individually, from the class of hoto-conductive insulators.

The resins used in the present invention are obtained by condensing p,p-dichlorodiphenylsulfone with a suitable salt of a dihydroxy organiccompound. Best results are obtained when using salts of bisphenol-A,2,2-(4 bishydroxy-phenyl)-propane, in the preparation of the resin andthis is considered to be the preferred dihydroxy com pound. Otherhydroxy-containing compounds such as resorcinol, hydroquinone glycols,glycerol, and mixtures thereof may be used in mixture with or in lieu ofthe hydroxy alkanes if desired. The di(mono-hydroxyaryl)-v alkanes,however, are preferred; with as noted above hisphenol-A being the mostpreferred embodiment.

Any suitable di-(mono-hydroxy) alkane may be used in this invention.Typical alkanes are:

(4,4'-dihydroxydiphenyl)-methane,

2,2-(4 bis-hydroxy phenyl)-propane, 1,l-(4,4'-dihydroxydiphenyl)cyclohexane,

l, l 4,4'-dihydroxy-3,3 -dimethyl-diphenyl) cyclohexane, 1, l2,2-dihydroxy-4,4'-dimethyl-diphenyl -butane,2,2-(2,2-dihydroxy-4,4'-di-tert-butyl-diphenyl)-propane,1,1-(4,4-dihydroxy-diphenyl)-1-phenyl-ethane,2,2-(4,4'-dihydroxydiphenyl) butane, 2,2-(4,4'-dihydroxy-diphenyl)pentane, 3,3-(4,4-dihydroxy-diphenyl) pentane,2,2-(4,4'-dihydroxy-diphenyl)-hexane,

5 3,3- (4,4-dihydroxy-diphenyl -hexane, 2,2- (4,4-dihydroxy-diphenyl-4-methyl-pentane (dihydroxy-diphenyl) -heptane, 4,4(4,4-dihydroxy-diphenyl -heptane, 2,2-(4,4-dihydroxy-diphenyl)-tridecane, 2,2- 4,4-dihydroxymethyl-diphenyl -prop ane,2,2-(4,4'-dihydroxy-3-methyl-3'-isopropyl-dipheny1) butane,2,2-(3,5,3,5'-tetrachloro-4,4-dihydroxy-diphenylpropane,2,2-(3,5,3,5-tetrabromo-4,4-dihydroxy-diphenyl)- propane, (3,3-dichloro-4,4'-dihydroxy-diphenyl) -methane, and(2,2-dihydroxy-5,5'-difluoro-diphenyl)methane, and l, l-(4,4'-dihydroxy-diphenyll-phenyl) -ethane, and mixtures thereof.

Any suitable Lewis acid can be complexed with the above notedpolysulfone resins to form the desired photoconductive material. Whilethe mechanism of the complex chemical interreaction involved in thepresent process is not completely understood, it is believed that acharge transfer complex is formed having absorption bands characteristicof neither of the two components considered individually. The mixture ofthe two non-photoconductive components seems to have a synergisticeffect which is much greater than additive.

Best results are obtained when using these preferred Lewis acids:2,4,7-trinitro-9-fiuorenone,9-(dicyanomethylene)-2,4,7-trinitrofluorene,2,3-dichloro-1,4-naphthaquinone and mixtures thereof.

Other typical Lewis acids include: quinones, such as p-benzo-quinone,2,6-dichlorobenzoquin0ne, chloranil, naphthoquinone-( 1,4),2,3-dichloronaphthoquinone-( 1,4), anthraquinone, Z-methylanthraquinone,1,4dimethylanthraquinone, l-chloroanthraquinone,anthraquinone-Z-carboxylic acid, 1,S-dichloroanthraquinone,I-chloro-4-nitroanthraquinone, phenanthrene-quinone, acenapthenequinone,pyranthrenequinone, chrysenequinone, thio-naphthene-quinone,anthraquinone-1,8-disulfonic acid and anthraquinone-2-aldehyde;triphthaloly'benzene-aldehydes, such as 'bromal, 4-nitrobenzaldehyde,2,6-dichlorobenzaldehyde-2, ethoxy-l-naphthalidehyde,anthracene-9-aldehyde, pyrene-3-aldehyde, oxindole-3-aldehyde,pyridine-2,6-dialdehyde, biphenyl-4aldehyde; organic phosphonic acids,such as 4-chloro-3-nitro=benzene-phosphoric acid nitrophenols,

such as 4-nitrophenol, and picric acid; acid anhydrides, for example,aceticanhydride, succinic anhydride, maleic anhydride, phthalicanhydride, tetrachlorophthalic anhydride, perylene3,4,9,10-tetracarboxylic acid and chrysene-2,3,8,9-tetracarboxylicanhydride,

metal halides of the metals and metalloids of the groups 1B, II throughto Group VIII of the periodical system for example:

aluminum chloride,

zinc chloride,

ferric chloride tin tetrachloride (stannic chloride), arsenictrichloride,

stannous chloride,

antimony pentachloride,

magnesium chloride,

magnesium bromide,

calcium bromide,

calcium iodide,

strontium bromide,

chromic bromide,

manganous chloride,

cobaltous chloride,

cobaltic chloride,

cupric bromide,

ceric chloride,

thorium chloride,

arsenic tri-iodide; -b0r0n halide compounds, for example: borontrifiuoride, and

boron trichloride;

and ketones, such as acetophenone,

'benzophenone,

2-acetylnaphthalene,

benzil benzoin,

S-benzoyl acenaphthene,

biacenedione,

9-acetyl-anthracene, 9-benzoylanthracene, 4-(4-dimethyl-amino-cinnamoyl)-l-acety1benzene, acetoacetic acid anilide,

indandione-( 1,3),

( 1-3-diketo-hydrindene) acenaphthene quinone-dichloride, anisil,

2,2-pyridil, and

furil.

Additional Lewis acids include mineral acids such as the hydrogenhalides, sulphuric acid and phosphoric acid; organic carboxylic acids,such as acetic acid and the substitution products thereof,

monochloro-acetic acid, I

dichloroacetic acid,

trichloro-acetic acid,

phenylacetic acid, and

6-methylcoumarinylacetic acid (4);

maleic acid,

cinnamic acid,

'benzoic acid,

l-(4diethyl-amino-benzoyl) benzene-Z-carboxylic acid,

phthalic acid, and

tetra-chlorophthalic acid,

alpha=beta-dibromo-beta-formyl-acrylic acid (mucobromic acid),

dibromomaleic acid,

2 bromo-benzoic acid,

gallic acid,

3-nitro-2-hydroxyl-I benzoic acid,

2-nitro phenoxy-acetic acid,

Z-nitrobenzoic acid,

B-nitro-benzoic acid,

4-nitro-'benzoic acid,

3-nitro-4-ethoxy-benzoic acid,

2-chloro-4-nitro-l-benzoic acid,

2-chloro-4-nitro-l benzoic-acid,

3-nitro-4-methoxy-benzoic acid,

4-nitro-l-methyl-benzoic acid,

Z-chloro-S-nitro-l-benzoic acid,

7: 3-bhloro-6-nitro-1 benzoic acid, 4-ehlo ro-3 nitro-1=benzoic acid,5-chloro-3-nitro-2-hydroxy-'benzoic acid, 4-chloro-2-hydroxy benzoicacid, 2,4-dinitro-1-benzoic acid, 2-bromo-5-nitro benzoic acid,4-chlorophenyI-acetic acid, 2-chloro-cinnamic acid, Z-cyanO-cinnamicacid, 2,4-dichloro benzoic acid, 3,5-dinitro-benzoic acid,3,5-dinitro-salycylic acid, malonic acid, mucic acid,

- acetosalycylic acid,

benzilic acid,

'butane-tetra-carboxylic acid,

citric acid,

cyano-acetic acid,

cyclo-hexane-dicarboxylic acid, cyclo-hexane-carboxylic acid,

9,10-dichlorostearic acid,

fumaric acid,

itanonic acid,

levulinic acid,

(levulic acid) malic acid,

succinic acid,

alpha-bromo-stearic acid,

citraconic acid,

dibromo-succinic acid, pyrene-2,3,7,8-tetra-carboxylic acid,

tartaric acid;

organic sulphonic acids, such as 4-toluene sulphonic acid, and

benzene sulphonic acid, 2,4-dinitro-1-methyl-benzene-6-sulphonic acid,2,6-dinitro-1-hydroxy-benzene-4-sulphonic acid,2-nitro-1-hydroxy-benzene-4-sulphonic acid,4-nitro-1-hydroxy-Z-benzene-sulphonic acid,3-nitro-2-methyl-1-hydroxy-benzene-S-sulphonic acid,6-nitro-4-methyl-1-hydroxy-benzene-2-sulphonic acid, 4-chloro-l-hydroxybenzene-3-sulphonic acid, 2-chlor0-3-nitro-l-methyl-benzene-5-sulphonicacid, and 2-chloro-1-methyl=benzene-4-sulphonic acid.

The following examples will further define the present invention. Partsand percentages are by weight unless otherwise indicated. The examplesbelow should be considered to illustrate various preferred embodimentsof the present invention:

In each of Examples I-XIII the substance to be evaluated is coated bysuitable means onto a conductive substrate and dried. The coated plateis connected to ground and the layer is electrically charged in the darkby a corona discharge device (positive or negative) to saturationpotential using a needlepoint scorotron powered by a high voltage powersupply manufactured by High Volt Power Supply Company, CondenserProducts Division, Model PS-l0-1M operating at 7 kilovolts whilemaintaining the grid potential at 0.9 kilovolt using a Kepco,Incorporated regulated D.C. supply (O1500 volts). Charging time is 15seconds. Such corona charging is described in detail by Carlson in U.S.Patent 2,588,699.

The electrostatic potential due to the charge is then measured with atransparent electrometer probe without touching the layer or atfectingthe charge. The signal generated in the probe by the charged layer isamplified and fed into a Moseley Autograf recorder, Model 680.- Thegraph directly plotted by the recorder indicates the magnitude of thecharge on the layer and rate of decay of the charge with time. After aperiod of about 15 seconds, the layer is illuminated by shining lightonto the layer through the transparent probe using an American OpticalSpencer microscope illuminator having a GE 1493 medical typeincandescent lamp operating at2800 K. color temperature. Theillumination level is measured with a Weston Illumination Meter, ModelNo. 756, and is recorded in the table. The light discharge rate is'meas=ured for a period of 15 seconds or until a steady residual potential isreached.

The numerical difference in the rate of discharge of the charge on thelayer with time in the light minus the rate of discharge of the chargeon the layer in the dark is considered to be a measure of the lightsensitivity of the layer.

Practical tests are also made on each material under study which shownphotoconductivity. An electrophotographic image is produced by chargingthe material by corona discharge, exposing the material by projection'toa light-and-shadow image and developing the electrostatic latent imageby cascade using a commercial developer. Details of this procedure aregiven in Example I.

' EXAMPLE I About 10 .parts of Bakelite Polysulfone P1700 (manufacturedby the Union Carbide Corporation) which has the following molecularstructure.

is dissolved in about 200 parts dichloromethone. To this solution isadded a solution of about 3 parts 2,4,7-trinitro- 9-fiuorenone in about50 parts cyclohexanone. The mixture is agitated to insure uniformity.

The above preparedsolution is flow coated onto bright finished 1145-H19aluminum foil made by the Aluminum Company of America and oven dried atabout C. for about 10 minutes. The dried coating thickness is about 5microns.

A 6 x 6 inch portion of the above prepared plate is negatively chargedto about 450 volts by means of a corona discharge device, exposed forabout 15 seconds by projection using a Simmons Omega D3 enlargerequipped with an f/4.5 lens and a tungsten light source operating at2950 K. color temperature. The illumination level at the plate is aboutfour foot candles as measured with a Weston Illumination Meter Model No.756. The plate is then developed by cascade as described by Walkup inU.S. Patent 2,618,551. The developed image is then electrostaticallytransferred to a receiving sheet and fused by the method described bySchatfert in U.S. Patent 2,576,047. The image on the sheet is of goodquality and corresponds to the projected image. The plate is thencleaned of residual toner and is reused as by the above describedprocess.

Another portion of the above prepared plate is electrometered aspreviously described and the results are tabulated. See Table I.

EXAMPLE II A coating solution is prepared as described in Example Iabove except that the polysulfone is Bakelite Polysulfone P2300 (UnionCarbide). This polysulfone has a structure similar to that given inExample I, but has a higher 'molecular weight. The above preparedsolution is coated A coating solution is prepared as described inExample I above except that the polysulfone is Bakelite PolysulfoneP3500 (Union Carbide). This resin has a structure similar to that shownin Example I, but has a still higher molecular weight. The solution thusprepared is applied onto a conductive substrate as previously describedand dried. A positive image corresponding to the original is produced,

1 EXAMPLE 1x About 2 milligrams of Brilliant Green Special dye, C1. No.662, a triphenyl methane (Allied Chemical) is added to a coatingsolution prepared as described in Example I having good density andcontrast and resolution in excess 5 of 20 line pairs/mm. A coated plateis then electromaboveflThe sohmon 1s PE onto conduciwe Substrate eteredas described and the data are tabulated. See and A xerogrfipfilc imageproduced as m Example I is of excellent quality. A plate iselectrometered and the Table I.

EXAMPLE N data are tabulated. See Table I. This illustrates thatincreased visible light sensitivity A coating Solution is P p asdeSCflbed 111 Example may be obtained by the addition of sensitizingdyes to the 1, except that about 3 parts 9-(dicyanomethylene)-2,4,7-composition, trinitrofluorene is used in place of the 2,4,7-trinitro-9-EXAMPLE X fiuorenone. The solution thus prepared is applied onto aconductive substrate as previously described and dried. A {Xbout onegram of Luclte 2042 ethyl methacrylate portion of the plate is exposedand developed as in Ex- Tesln manufactllfed PY Du POIlt d6 Nem011f ampleI, producing a positive image of good quality Company, Inc., isdissolved 1n a solvent blend consisting other portion of the plate isthen electrometered and the of about 10 Parts methyl ethyl ketone, aboutP data tabulatedin'rable benzene, about 1 part acetone and about 2 partsdiethyl ketone. The mixture is agitated by a stirrer until the resinEXAMPLE V is fully dissolved in the solvent blend. A plate is coated,dried, charged, exposed and developed The above solution is applied ontoan aluminum plate as in Example IV, except that here the Lewis acid usedby suitable means and dried. is 2,3-dichloro-1,4-naphthoquinone. Theimage produced The above plate is electrometered and the results are onthis plate is of excellent quality. A portion of the plate I tabulated.See Table I. This plate is used as a control is electrometered and theresults recorded in Table I. binder 1n Examples VII-X.

The data resulting from Examples I-V show that poly- This indicates thatLucite 2042 is non-photoconductive. siulfone redsins are photoconductivewhere combined with EXAMPLE XI ew1s am 3.

EXAMPLE VI About 0.25 part of 2,4,7-trinitrotluorenone is added to 1 acoating solution prepared as described in Example X A coatmg SQIHUOD 1sPTeParQd aigescnbad P Exam? e above. The solution is applied onto aconductive subabov? but wlthout any fi e The resm solunon strate asdescribed and dried. The plate is electrometered is applied onto aconductive substrate and dried. The and the data are tabulated See TableL above prepared plate is electrometered and the results tabulated. SeeTable I. The polysulfone resin coating with- EXAMPLE XII out Lewis acidis thus found to be non-photoconductive. About 025 partQ-(dicyanomethylene)-2,4,7-t1initf0- EXAMPLE V11 fiuorenone is added toa coating solution prepared as 1 described in Example X above. Thesolution is applied A coatmg 591M011 PIePaIPd fi aig i P n onto aconductive substrate as described and dried. The F but Wlthout Y aclde 1S0 15 40 plate is electrometered and the data are tabulated. See appliedonto a conductive substrate and timed. Thls plate Table L is charged,exposed and electrometered as in Example II. EXAMPLE As shown in TableI, this plate is non-photoconductive.

About 2 milligrams of Brilliant Green dye is added to EXAMPLE VH1 acoating solution prepared as described in Example X A coating solutionis prepared as described in Example above. The solution is applied ontoa conductive substrate III above, but with no Lewis acid. The resinsolution is and dried. The plate is electrometered and the results arecoated onto a conductive substrate and wired. This plate tabulated. SeeTable I. is charged, exposed and electrometered as in Example 111.Examples X-XIII show that the Lewis acids and sen- As shown by theresults tabulated in Table I, the plate is sitizing dyes tested arenon-photoconductive in an inert non-photoconductive in the absence ofLewis acid. binder, such as Lucite 2042.

TABLE I Initial Light Dark Residual Illumina- Sensitivity ExamplePotential Discharge Discharge Potential tion (foot volts/ (volts)(volts/sec.) (volts/sec.) after 15sec. candles) f-CrSGC.)

(volts) I +500 24. 0 4. 0 +230 134 1. 3 -040 43. 0 5. 0 -205 134 3. 2 II+540 22. 4 6. 4 +310 134 1. 2 -550 32. 0 4.4 -310 134 1. 3 III +430 32.0 4. 0 +220 134 2. 1 -570 70. 0 4. 0 -220 134 5. 3 Iv +220 24. 0 3. 0+305 57 23. 1 -350 50. 1 24. 0 57 50. 4 V +400 10. 7 4. 0 +410 57 11.7-500 10.7 2. 2 +470 57 14. 0 VI +530 0 0 +530 134 0 -710 0 0 -710 134 0VII +770 0 0 +770 134 0 -000 0 o -300 134 0 VIII +430 0 0 +430 134 0-570 0 0 -570 134 0 1x +430 50. 0 13. 3 +150 57 74. s -515 11s. 0 12. 0-100 57 170. 0 X +400 4. 4 4. 4 304 0 -500 5.3 5.3 420 130 0 X1 +310 3.33.3 200 130 0 -310 3.3 3.3 200 13a 0 XII +330 3. 0 3. 0 335 135 0 +4704. 0 4. 0 410 130 0 XIII +350 2.7 2.7 310 130 0 -325 1. 0 1. 0 315 130 0In the above table, sensitivity represents the initial dis charge rateupon illumination in volts/100 foot candle seconds corrected for therate of dark discharge. As shown by Examples I-IV, a mixture of apolysulfone resin and a Lewis acid is photoconductive. Examples V-VHshow that a polysulfone resin used alone, with no Lewis acid, is notphotoconductive. Example VIII indicates that a polysulfone resin-Lewisacid complex can be dye sensitized. As shown by Example IX, Lucite2042,.is not photoconductive. Examples X-XII show that the Lewis acidsand sensitizing dyes used in Examples I-IV and VIII are notphotoconductive in an inert Lucite binder.

Although specific materials and conditions were set forth in the aboveexamples, these were merely illustrative of the present invention.Various other compositions, such as the typical materials listed aboveand various conditions where suitable, may be substituted for thosegiven in the examples with similar results. The photoconductivecomposition of this invention may have other materials or colorantsmixed therewith to enhance, sensitize, synergize or otherwise modify thephotoconductive properties of the composition. The photoconductivecompositions of this invention, where suitable,'may be used in otherimaging processes, such as those disclosed in copending applicationsSer. Nos. 384,737, now US. Patent 3,384,565; 384,- 680; and 384,681;both now abandoned, Where their electrically photosensitive propertiesare beneficial.

Many other modifications of the present invention will occur to thoseskilled in the art upon a reading of this disclosure. These are intendedto be encompassed within the spirit of this invention.

What is claimed is:

1. A photoconductive charge transfer complex material comprising amixture of a Lewis acid and a polysulfone resin having repeating unitsof the following general formula:

wherein:

X and Y are each selected from the group consisting of hydrogen andalkyl radicals, and wherein the total number of carbon atoms in X and Yis up to 12; and

n is an integer having a value of at least 2, said photoconductivecharge transfer complex having at least onenew absorption band within arange of from about 3200 to about 7500 Angstrom units.

2. The photoconductive charge transfer complex material of claim 1comprising from about 1 to about 100 parts of said resin for every onepart of said Lewis acid.

3. The photoconductive charge transfer complex material of claim 1wherein said resin comprises the reaction product ofp,p-dichlorodiphenylsulfone and 2,2-bis-(4- hydroxy-phenyl) propane.

4. The photoconductive charge transfer complex material of claim 3comprising from about 1 to about 100 parts of said resin for every onepart of said Lewis acid.

5. The photoconductive charge transfer complex material of claim 1wherein said Lewis acid is selected from the group consisting of2,4,7-trinitro-9-fiuorenone, 9-(dicyanomethylene-2,4,7-trinitro-fluorene, 2,3-dichloro-1,4- naphthaquinone, and mixturesthereof.

6. The charge transfer complex material of claim 1 wherein said Lewisacid comprises 2,4,7-trinitro-9-fluo renone.

7. A process for the preparation of a photoconductive charge transfercomplex material which comprises mixing a Lewis acid and a polysulfoneresin having repeating units of the following formula:

wherein:

X and Y are each selected from the group consisting of hydrogen andalkyl radicals, and wherein the total number of carbon atoms in X and Yis up to 12; and

n is an integer having a value of at least 2, said charge transfercomplex having at least one new absorption band within a range of fromabout 3200 to about 7500 Angstrom units. I,

8. The process of claim 7 wherein from about 1 to about 100 parts ofresin are mixed for every one part of Lewis acid.

9. Theprocess of claim 7 wherein said resin comprises the reactionproduct of p,p'-dichlorodiphenylsulfone and 2,2-bis-(4-l1ydroxy-phenyl)propane.

10. The process of claim 7 wherein said Lewis acid is selected from thegroup consisting of 2,4,7-trinitro-9-fluorenone,9-(dicyanomethylene)-2,4,7-trinitro-fluorene, 2,3

dichloro-1,4-naphthaquin0ne, and mixtures thereof.

11. The process of claim 7 wherein said Lewis acid comprises2,4,7-trinitro-9-fluorenone.

12. An electrophotographic plate comprising a support substrate havingfixed to the surface thereof a photoconductive charge transfer complexmaterial comprising a mixture of a Lewis acid and a polysulfone resincomprising recurring units having the formula:

wherein:

X and Y are each selected from the group consisting of hydrogen andalkyl radicals, and wherein the total number of carbon atoms in X and Yis up to 12; and

n is an integer having a value of at least 2, said photoconductivecharge transfer complex having at least one new absorption band withinthe range of from about 3200 to about 7500 Angstrom units.

13. The electrophotographic plate of claim 12 wherein said Lewis acid isselected from the group consisting of 2,4,7-trinitro-9-fluorenone,9-(dicyanomethylene)-2,4,7- trinitro-fluorene,2,3-dichloro-1,4-naphthaquinone, and mixtures thereof.

'7 14. The electrophotographic plate of claim 12 wherein said Lewis acidcomprises 2,4,7-trinitro-9-fluorenone.

15. The electrophotographic plate of claim 12 comprising from about 1 toabout 100 parts of said resin for every one part of said Lewis acid.

a 16. A method of forming a latent electrostatic charge patterncomprising charging the electrophotographic plate of claim 12 andexposing said plate to a pattern of activating electromagneticradiation.

17. A method of forming a latent electrostatic pattern wherein the plateof claim 12 is electrostatically charged in an image pattern.

18. Anelectrophotographic process wherein the plate of claim 12 iselectrically charged, exposed to an image pattern. to be reproduced anddeveloped with electrically attractable marking particles.

19. An electrophotographic process wherein the plate of claim 12 iselectrostatically charged in an image pattern and developed withelectrically attractable marking particles.

20. The process of claim 18 further including the steps "of transferringsaid marking particles to the surface of a 13 receiving sheet, andrecharging, exposing and developing said plate to produce at least morethan one copy of the original.

21. The process of claim 19 further including the steps of transferringsaid marking particles to the surface of a receiving sheet, andrecharging, exposing and developing 5 said plate to produce at leastmore than one copy of the original.

14 References Cited UNITED STATES PATENTS 3,287,121 11/1966 Hoegl 96l.53,287,122 11/1966 Hoegl 961.5

I. TRAVIS BROWN, Primary Examiner.

J. C. COOPER III, Assistant Examiner.

